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path: root/libavcodec/xsubenc.c (plain)
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1/*
2 * DivX (XSUB) subtitle encoder
3 * Copyright (c) 2005 DivX, Inc.
4 * Copyright (c) 2009 Bjorn Axelsson
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include "avcodec.h"
24#include "bytestream.h"
25#include "put_bits.h"
26
27/**
28 * Number of pixels to pad left and right.
29 *
30 * The official encoder pads the subtitles with two pixels on either side,
31 * but until we find out why, we won't do it (we will pad to have width
32 * divisible by 2 though).
33 */
34#define PADDING 0
35#define PADDING_COLOR 0
36
37/**
38 * Encode a single color run. At most 16 bits will be used.
39 * @param len length of the run, values > 255 mean "until end of line", may not be < 0.
40 * @param color color to encode, only the lowest two bits are used and all others must be 0.
41 */
42static void put_xsub_rle(PutBitContext *pb, int len, int color)
43{
44 if (len <= 255)
45 put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
46 else
47 put_bits(pb, 14, 0);
48 put_bits(pb, 2, color);
49}
50
51/**
52 * Encode a 4-color bitmap with XSUB rle.
53 *
54 * The encoded bitmap may be wider than the source bitmap due to padding.
55 */
56static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
57 int linesize, int w, int h)
58{
59 int x0, x1, y, len, color = PADDING_COLOR;
60
61 for (y = 0; y < h; y++) {
62 x0 = 0;
63 while (x0 < w) {
64 // Make sure we have enough room for at least one run and padding
65 if (pb->size_in_bits - put_bits_count(pb) < 7*8)
66 return -1;
67
68 x1 = x0;
69 color = bitmap[x1++] & 3;
70 while (x1 < w && (bitmap[x1] & 3) == color)
71 x1++;
72 len = x1 - x0;
73 if (PADDING && x0 == 0) {
74 if (color == PADDING_COLOR) {
75 len += PADDING;
76 x0 -= PADDING;
77 } else
78 put_xsub_rle(pb, PADDING, PADDING_COLOR);
79 }
80
81 // Run can't be longer than 255, unless it is the rest of a row
82 if (x1 == w && color == PADDING_COLOR) {
83 len += PADDING + (w&1);
84 } else
85 len = FFMIN(len, 255);
86 put_xsub_rle(pb, len, color);
87
88 x0 += len;
89 }
90 if (color != PADDING_COLOR && (PADDING + (w&1)))
91 put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);
92
93 avpriv_align_put_bits(pb);
94
95 bitmap += linesize;
96 }
97
98 return 0;
99}
100
101static int make_tc(uint64_t ms, int *tc)
102{
103 static const int tc_divs[3] = { 1000, 60, 60 };
104 int i;
105 for (i=0; i<3; i++) {
106 tc[i] = ms % tc_divs[i];
107 ms /= tc_divs[i];
108 }
109 tc[3] = ms;
110 return ms > 99;
111}
112
113static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
114 int bufsize, const AVSubtitle *h)
115{
116 uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
117 uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
118 int start_tc[4], end_tc[4];
119 uint8_t *hdr = buf + 27; // Point behind the timestamp
120 uint8_t *rlelenptr;
121 uint16_t width, height;
122 int i;
123 PutBitContext pb;
124
125 if (bufsize < 27 + 7*2 + 4*3) {
126 av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
127 return -1;
128 }
129
130 // TODO: support multiple rects
131 if (h->num_rects != 1)
132 av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
133
134#if FF_API_AVPICTURE
135FF_DISABLE_DEPRECATION_WARNINGS
136 if (!h->rects[0]->data[0]) {
137 AVSubtitleRect *rect = h->rects[0];
138 int j;
139 for (j = 0; j < 4; j++) {
140 rect->data[j] = rect->pict.data[j];
141 rect->linesize[j] = rect->pict.linesize[j];
142 }
143 }
144FF_ENABLE_DEPRECATION_WARNINGS
145#endif
146
147 // TODO: render text-based subtitles into bitmaps
148 if (!h->rects[0]->data[0] || !h->rects[0]->data[1]) {
149 av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
150 return -1;
151 }
152
153 // TODO: color reduction, similar to dvdsub encoder
154 if (h->rects[0]->nb_colors > 4)
155 av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
156
157 // TODO: Palette swapping if color zero is not transparent
158 if (((uint32_t *)h->rects[0]->data[1])[0] & 0xff000000)
159 av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
160
161 if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
162 av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
163 return -1;
164 }
165
166 snprintf(buf, 28,
167 "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
168 start_tc[3], start_tc[2], start_tc[1], start_tc[0],
169 end_tc[3], end_tc[2], end_tc[1], end_tc[0]);
170
171 // Width and height must probably be multiples of 2.
172 // 2 pixels required on either side of subtitle.
173 // Possibly due to limitations of hardware renderers.
174 // TODO: check if the bitmap is already padded
175 width = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
176 height = FFALIGN(h->rects[0]->h, 2);
177
178 bytestream_put_le16(&hdr, width);
179 bytestream_put_le16(&hdr, height);
180 bytestream_put_le16(&hdr, h->rects[0]->x);
181 bytestream_put_le16(&hdr, h->rects[0]->y);
182 bytestream_put_le16(&hdr, h->rects[0]->x + width -1);
183 bytestream_put_le16(&hdr, h->rects[0]->y + height -1);
184
185 rlelenptr = hdr; // Will store length of first field here later.
186 hdr+=2;
187
188 // Palette
189 for (i=0; i<4; i++)
190 bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->data[1])[i]);
191
192 // Bitmap
193 // RLE buffer. Reserve 2 bytes for possible padding after the last row.
194 init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
195 if (xsub_encode_rle(&pb, h->rects[0]->data[0],
196 h->rects[0]->linesize[0] * 2,
197 h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
198 return -1;
199 bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field
200
201 if (xsub_encode_rle(&pb, h->rects[0]->data[0] + h->rects[0]->linesize[0],
202 h->rects[0]->linesize[0] * 2,
203 h->rects[0]->w, h->rects[0]->h >> 1))
204 return -1;
205
206 // Enforce total height to be a multiple of 2
207 if (h->rects[0]->h & 1) {
208 put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
209 avpriv_align_put_bits(&pb);
210 }
211
212 flush_put_bits(&pb);
213
214 return hdr - buf + put_bits_count(&pb)/8;
215}
216
217static av_cold int xsub_encoder_init(AVCodecContext *avctx)
218{
219 if (!avctx->codec_tag)
220 avctx->codec_tag = MKTAG('D','X','S','B');
221
222 avctx->bits_per_coded_sample = 4;
223
224 return 0;
225}
226
227AVCodec ff_xsub_encoder = {
228 .name = "xsub",
229 .long_name = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
230 .type = AVMEDIA_TYPE_SUBTITLE,
231 .id = AV_CODEC_ID_XSUB,
232 .init = xsub_encoder_init,
233 .encode_sub = xsub_encode,
234};
235
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